matrix multiply even and odd by different value

Question

Joseph 2014-12-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/166874-matrix-multiply-even-and-odd-by-different-value

评论： Joseph 2014-12-22

采纳的回答： per isakson

IMAG0397.jpg

在 MATLAB Online 中打开

Hi, given a matrix zj

    NL=4;NV=6;xiz=0.011e-3;f=1;
    zj=repmat((1:NL),NV,1)

Let i be the rows and j be the column elements. So I would like to multiply each element of zj by the following condition

    j*xiz % when i is odd
    a.*((-1)+2.*j)+(-1).*((-1)+f+j).*(2.*a+xiz) % when i is even

For clarification I've attached an image of this in maths form. Thanks,

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Answer 1

per isakson 2014-12-17

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https://ww2.mathworks.cn/matlabcentral/answers/166874-matrix-multiply-even-and-odd-by-different-value#answer_162566

编辑：per isakson 2014-12-17

在 MATLAB Online 中打开

Try this script

    NL=4;NV=6;xiz=0.011e-3;f=1;
    zj = repmat((1:NL),NV,1);
    a  = pi;
    [C,R]   = meshgrid( 1:size(zj,2), 1:size(zj,1) );
    is_odd  = isOdd( R );
    is_even = not( is_odd );
    out     = nan( size(zj) );
    out(is_odd) = zj(is_odd).* C(is_odd) .* xiz;
    out(is_even)= zj(is_even).* a.*((-1)+2.*C(is_even))+(-1) ...  
                  .*((-1)+f+C(is_even)).*(2.*a+xiz);

where

    function    iso = isOdd( val )
        % cred: Subject: Even/odd, From: us, Date: 23 Aug, 2007 15:21:31
        iso = logical( bitand( abs( val ), 1 ) );
    end

&nbsp

Comment

I tried to implement the description in your question, which doesn't fully agree with the "image" - I think.

"multiply each element of zj by the following condition" &nbsp I read multiply by factor.

However, my script should be a starting point.

The function, isOdd, throws an error if the input is not a whole number (and it is fast).

    >> isOdd( pi )
    Error using bitand
    Double inputs must have integer values in the range of ASSUMEDTYPE.
    Error in isOdd (line 11)
        iso = logical( bitand( abs( val ), 1 ) );